This invention relates to improvements in valves and pumps; in particular to improvements in pinch valves and to an improved pump incorporating features of such an improved valve.
A pinch valve typically consists of a flexible resilient cylindrical elastomeric sleeve disposed in a valve body in the form of a continuous tube, sleeve or the like, together with a means to constrict the sleeve so as to control or stop the flow of fluid through the pipe. Typically the sleeve is concentrically located within a rigid outer valve housing and suitable means are provided to impress a fluid under pressure between the sleeve and the rigid valve housing so that the sleeve is squeezed inwards and deformed or collapsed to provide a restricted fluid flow passage. The impressed fluid is typically a gas or liquid under pressure. When that pressure is released, the resilience of the elastomeric tube is relied upon to open the valve. The elastomeric sleeve typically comprises a fabric reinforcement embedded in synthetic rubber to support the valve closure against the introduced pressure. Higher valve delivery pressure capacity and the need for adequate resilience in the tube to induce suction at the valve inlet when opening, require increasing layers of fabric reinforcement and increased wall thickness for the tube. This leads to a consequent loss of flexibility to the point where the required wall thickness may become impractical for use as a pinch valve.
A duck-beak valve is a check valve form of the pinch valve that is closed in its relaxed condition with the outlet end of the sleeve unattached to the valve body. The fluid transiting the valve surrounds the inside and the outside of the sleeve, which opens when the valve inlet pressure sufficiently exceeds the valve outlet pressure.
The alternative use of flap type check valves have the problem that they are vulnerable to being held open by the entrapment of solids between the flap and the valve seat.
Thus, while a number of valve designs have been proposed, there remains a need for alternative designs.
It should be noted that any discussion of documents, acts, materials, devices, articles or the like which has been included in the present specification is solely for the purpose of providing a context for the present invention. It is not to be taken as an admission that any or all of these matters form part of the prior art base or were common general knowledge in the field relevant to the present invention as it existed before the priority date of each claim of this application.